Have I done a disclaimer yet? Well you all know I don't own Inuyasha and I'm not making any profit from this story except the pleasure i get from your reviews *hint hint*
To be selfish.
He did not see her in the brief time she stayed in the Western Lands before Touga eventually decided to let her go. He loved her yes, and she loved him, and that was the problem, if he saw her again he was sure that he would just take her and run. But he could not do that, because then he would be no better than the Inutaisho. He just needed time to get a hold of himself before seeing her again, but before he got the chance she was taken away from him, back down that well in the forest that took her to the future.
Then it all made sense, he had waited too long, he should have just taken her, because even if she was angry at least he would have her. Was it really so bad to want something for himself for a change. He was always giving; he gave up his childhood to train to take over a kingdom so his father could retire. He gave up his sister Shiori for the studies he had to take to make a good ruler, and he was expected to give up his freedom and a chance to marry someone he wanted to mate someone who would be respected and birth him powerful kits.
But he was tired of being selfless; he wanted something for himself, someone: her. Was it so bad? WHY WAS IT SO BAD? He wasn't asking for much, he really wasn't, he just wanted one person, her, that dog had so much already, a mate, a pup, and Hiro, he could have any girl he wanted (apart from her) if he cared to notice. He did not want to let her go, he wanted her, and he was not going to let that dog have her, so he was going to wait for her. If it took several hundred years he would wait for her, and by Kami he would get to her first.